1. Technical Field
This invention generally relates to devices for summing or splitting component frequencies of a signal, and more specifically to a space qualifiable, high performance diplexer configured in distributive form which works as either a summer or a splitter.
2. Background Art
A diplexer is a device which separates a received signal into two frequency ranges within the received signal. Conventional diplexers comprise discrete circuit components to bandpass, highpass or lowpass filter a received signal into two frequency ranges.
Circuitry for use on a satellite must be space qualified to withstand the rigorous conditions of the launch and of the space environment. Some considerations for space qualification include the weight and size added to a satellite by the circuit and the circuit""s ability to survive extreme vibration, very wide temperature variations and the environmental and radiation contaminations of space over time. Conventionally, the manufacture of discrete components which meet the criteria set for space qualification is expensive, and discrete component elements are more likely to fail in space than elements without discrete components.
Signal filters for use in space have conventionally been fabricated using a ceramic-based diplexer. Ceramic-based diplexers include a diplexer cavity which has been laser-trimmed to tune the cavity like a wave guide to selectively pass only desired frequencies. While widely used commercially, however, ceramic-based diplexers are generally more bulky and heavy than circuit boards (about the size of a large desk phone), and are prone to damage from temperature cycles and aging. Over time, after being exposed to the extreme temperatures and conditions of space, ceramic-based diplexers tend to crack and their center frequencies tend to drift up rendering them ineffective for their intended purpose. For space applications, failed components is a particular problem because the satellites are not readily accessible for repairs and maintenance. Repair of satellite components, once in space, is expensive.
Thus, there is a need for a non-ceramic-based diplexer which is small and light weight without discrete components which can endure the rugged conditions required to qualify for space use. There is also a need for a small, high performance diplexer capable of handling high frequencies.
The present invention relates to a diplexer for summing or splitting a plurality of frequency bands through a plurality of distributive resonators joined by a common conductor. A specific embodiment of the invention includes a diplexer with two resonators configured and tuned to each filter one of the L1 or L2 signals and reflect the other. Through impedance matching in each of the respective resonator branches for the frequency to pass within the branch, high signal quality is maintained with low insertion loss. By using a printed circuit board with a ground plane, cross-talk is minimized. The resulting diplexer is tunable, has high signal isolation, has low insertion loss, and may be used reciprocally.
Specific applications for the invention described include use of a distributively formed diplexer within a signal receiver, a signal transmitter and an antenna array. The diplexer""s small size and weight, and its resistance to radiation and environmental contamination also make it ideal for use in satellite applications, and particularly for use with GPS.
The foregoing and other features and advantages of the present invention will be apparent from the following more particular description of the particular embodiments of the invention, as illustrated in the accompanying drawings.